1. Field of the Invention
The present invention relates to a drive member provided with a spiral groove for intermittently driving another member upon intermitten rotation of the drive member.
2. Description of Prior Art
FIG. 1 is a schematic diagram showing the arrangement of a drive mechanism provided with an intermittent drive member 4 formed with a spiral groove 9. The drive member 4 is supported between a bearing 2 and a coupling 3 connecting it to a drive motor 1 which may be rotated intermittently in either direction.
A guide bar 5 is provided in parallel to the screw member 4, and a movable member 6 is slidably fitted onto the guide bar 5. A tip portion 8 connected at the lower end portion of the movable member 6 through a plate spring 7 is slidably fitted into the spiral groove 9 formed in the outer periphery of the drive or screw member 4. Thus, the movable member 6 is adapted to reciprocate within a predetermined range by being guided by the guide bar 5, in response to te forward/backward rotation of the screw member 4.
When it is necessary to drive the movable member 6 intermittently in predetermined intervals, the motor 1 is intermittently energized to rotate the screw that a spiral groove 9 has a uniform or the same leading angle .THETA. over the entire circumference as shown in FIG. 2, so that the spiral groove 9 becomes linear when it is developed. Therefore, when it was required to intermittently stop the movable member 4, for example, at eight portions, that is at the revolution angles of 0.degree., 45.degree., 90.degree., 135.degree., 180.degree., 225.degree., 270.degree., and 315.degree. of the screw member 4, there has been a problem in reliability because there were variations in revolution angles of the screw member 4 or because of shift in control of rotation of the same so that the position of the movable member 6 might come off to thereby make it impossible to stop the movable member 6 at proper positions. Further, there was another problem that an error in feeding quantity was apt to be generated due to offset in controlling the revolution of the motor 1 as described above, so that in order to reduce such offset, it was necessary to employ a highly accurate, that is very expensive, motor.